Method and system for VLAN aggregation

US007792058B1

(12) Ulllted States Patent

(10) Patent N0.:

Yip et al. (54)

(75)

US 7,792,058 B1

(45) Date of Patent:

AGGREGATION

METHOD AND SYSTEM FOR VLAN

5,793,763 A 5,802,106 A

Inventors: Michael Yip, Sunnyvale, CA (US);

5’862’452 A

1/1999 Cudak et a1’

5’909’686 A

6/1999 Muller et 31'

Shehzad T. Merchant, Mountain View,

*Sep. 7, 2010

8/1998 Mayes et al. 9/1998 Packer

CA (US); Kenneth T. Yin, Rumson, NJ

(US); Eric Knudstrup, Saratoga, CA (US)

.

(Continued)

(73) Ass1gnee: Extreme Networks, Inc., Santa Clara, CA (US) .

(*)

_

.

Nonce'

.

.

OTHER PUBLICATIONS _

IEEE Std 802.1Q-l998, “IEEE Standards for Local and Metropolitan

SubJeCt. to any dlsclalmer’. the term Ofthls

Area Networks: Virtual Bridged Local Area Networks,” New York,

patent is extended or adjusted under 35 U.S.C. l54(b) by 770 days.

NeWYOrk 1999 ’ '

C t' d ( on mue )

This patent is subject to a terminal dis-

claimer.

Primary ExamineriDaniel J. Ryman

'

Assistant ExamineriNishant B Divecha

(21) Appl' NO" 11/050’165

(74) Attorney, Agent, or FirmiBlakely Sokoloff Taylor &

(22)

Zafman

Filed:

Feb. 2, 2005 Related US. Application Data

(57)

ABSTRACT

(63)

Continuation of application No. 09/595,608, ?led on

(51)

Jun‘ 16’ 2000’ HOW Pat‘ NO‘ 6914905‘ Int Cl H04L 12/28 (200601)

A method and system for an aggregated virtual local area network (VLAN) architecture in which several VLANs in a network share the same default router address and subnet

(52)

H04L 12/56 (200601) H04] 3/24 (200601) H04] 3/26 (2006.01) US. Cl. ..................... .. 370/255; 370/390; 370/392;

mask, but remain isolated from one another’ s network traf?c. Instead of the traditional method of assigning one subnet to a VLAN, eachVLAN is assigned only a portion of a subnet’ s IP address space, and is further grouped into a super-VLAN

370/395-53; 370/401; 370/432; 370/473

uniquely associated with that subnet. lntra-VLAN tra?ic is

(58)

Field Of Classi?cation Search ............... .. 370/390,

forwarded only to host IP addresses assigned to that same

370/432, 254: 255: 389: 392: 400: 401: 395:

VLAN according to a VLAN identi?er carried in the data

_

_

_

370/473

packet. Inter-VLAN traf?c is processed by a virtual router

See apphcanon ?le for Complete Search hlstory' (56) References Cited

interface which routes the data packet by applying the routing con?guration for the subnet uniquely associated with the super-VLAN, according to a super-VLAN identi?er carried in the data packet.

US. PATENT DOCUMENTS

5,732,078 A

3/1998 Arrango

5,737,333 A 5,742,604 A

4/1998 Civanlar et a1. 4/1998 Edsall et al.

22 Claims, 3 Drawing Sheets

SIM-‘92.1.1

sue 19 1 :11

1 \ 312 31a

1921 14-5

321

322

suavum R

192116-8 231

332

33a

US 7,792,058 B1 Page 2 Us. PATENT DOCUMENTS 5,910,955 5,926,463 5,938,736 5,946,308

A A A A

6/1999 7/1999 8/1999 8/1999

Nishimuraetal. Ahearn etalMuller er 91Dobbins er a1~

5,949,783 A

9/1999 Husak etal-

5,959,989 A 5,968,126 A

9/1999 Gleeson et al. 10/1999 Ekstrom et al.

6,178,455 6,178,505 6,181,681 6,181,699 6,182,226 6,182,228

B1 B1 B1 B1 B1 B1

1/2001 1/2001 1/2001 1/2001 1/2001 1/2001

Schutte etal. Schneideretal. Hiscocket 31‘ Crinion 6161. Reid 6161. BOdeIl 6161.

6,188,694 B1*

2/2001

F1116 6161. ................. .. 370/402

6,195,705 B1 6,202,114 B1

2/200l Leung 3/2001 Dun et 31‘

5,978,378 A *

11/1999 Van Seters er a1- -------- -- 370/401

6,208,649 B1*

3/2001

K161h ....................... .. 370/392

6,006,258 6,006,264 6,006,272 6,012,090 6,018,619 6,023,724

12/1999 12/1999 12/1999 V2000 V2000 2/2000

6,208,656 6,212,558 6,216,167 6,219,706 6,219,739 6,226,267

3/2001 4/2001 4/2001 4/2001 4/2001 5/2001

HfaSt?I 6161. Antur 6161. Momirov Fan 6161. 1311116161. Spinney 6161.

A A A A A A

Kalajan ColbyetalAravamudan et al. Chung eta1~ Allardetal Bhatia etal-

B1 B1 B1 B1 B1 B1

6,028,848 A

2/2000 Bhatiaetal

6,226,771 B1

5/2001 1111166161.

6,029,203 6,032,194 6,035,105 6,047,325

2/2000 2/2000 3/2000 4/2000

6,230,203 6,243,749 6,243,754 6,243,815

5/2001 6/2001 6/2001 6/2001

KOpefda 6161. Sitaraman 6161. 611611116161. Antur 6161. Chevalier et a1‘

A A A A

Bhatla @131 Gai er 91Mccloghrie er 91' Jain eta1~

B1 B1 B1 B1

6,049,834 A *

4/2000 Khabardar et al. ........ .. 709/242

6,246,669 B1

6/2001

6,052,803 A 6,058,106 A 6,058,431 A

4/2000 Bhatia @131 5/2000 Cudaketal 5/2000 Srisuresh @131

6,249,523 B1 6,252,888 B1 6,253,122 B1

6/2001 HfaSt?I 6161. 6/2001 11116116161. 6/2001 RaZavi 6161.

6,085,238 A *

7/2000 Yuasa et al. ............... .. 709/223

6,256,314 B1

7/2001

Rodrig et a1‘

6,088,356 6,094,435 6,094,659 6,098,172 6,104,696 6,104,700

7/2000 7/2000 7/2000 8/2000 8/2000 8/2000

6,262,976 6,266,707 6,269,099 6,430,621 6,526,052 6,553,028

7/2001 7/2001 7/2001 8/2002 2/2003 4/2003

McNamam BOdeIl 6161. 130161121 6161. Srikanth 6161. Rijhsinghani 6161. Tang et 31‘

A A A A A A

Hendelet al. Hoffman eta1~ Bhatia Cossetal Kadambietal Haddocket al.

B1 B1 B1 B1 B1 B1

6,105,027 A

8/2000 Schneider et 91-

6,614,787 B1*

9/2003 Jain 6161. ................. .. 370/390

6,108,330 A

8/2000 Bhatia 9491

6,614,792 B1

9/2003 Pazy 61 al.

6115378 A 6,118,768 A

9/2000 Hendel er a1~ 9/2000 Bhatia etal-

6,674,760 B1* 7,222,188 B1*

1/2004 Walrand 6161. ........... .. 370/411 5/2007 AIIleS 6161. ............... .. 709/238

6,118,784 6,119,162 6,119,171 6,128,657

A A A A

9/2000 9/2000 9/2000 10/2000

Tsuchiya et a1. Li et al. Alkhatib Okanoya et al.

OTHER PUBLICATIONS

B. Kantor, “Internet Protocol Encapsulation of AX.25 Frames,”

6,131,163 A

10/2000 Wiegel

Request for Comments: 1226, May 1991 (“RFC1226”).

6,141,749 A 6,147,995 A 6,151,316 A

10/2000 Coss et al. 11/2000 Dobbins et al. 11/2000 Crayford et al.

K. Egevang, “The IP Network Address Translator (NAT),” Request for Comments: 1631, May 1994, (“RFC1631”). W. Simpson, “IP in IP Tunneling,” Request for Comments 1853, Oct.

6,151,324 A *

11/2000 B61s616161. .............. .. 370/397

1995, (“RFC1853”).

6,154,446 6,154,775 6,154,839 6,157,647 6,157,955 6,167,052

11/2000 11/2000 11/2000 12/2000 12/2000 12/2000

C. Perkins, “1P Encapsulation Within 1P,” Request for Comments 2003, 061. 1996, (“RFC2003”). K. HamZeh, et al., “Point-to-Point Tunneling Protocol (PPTP),” Request for Comments 2637, Jul. 1999, (“RFC2637”). D. Farinacci, et al., “Generic Routing Encapsulation (GRE),” 1161111661161 (3611111161116 2784, M61. 2000, (“RFC2784”).

A A A A A A

6,167,445 A 6,170,012 B1

Kadambi et al. COSS 61 a1. AIIOW et 31 Hlls?k Narad et a1~ McNeilletal

12/2000 G31 61 al. 1/2001 Coss et al.

* cited by examiner

US. Patent

F

Sep. 7, 2010

u

l4_0

P2

P3

P4

P5

Switch 82

P6

WON/‘9W0 141

US 7,792,058 B1

Backbone Connecting Multiple Switches

Switch S1 P1

Sheet 1 of3

P1

P2

1.5_0 P5

P6

NW9 0 0 0

0

i

i

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V

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142

143

144

145

146

151

152

P3

P4

VLAN A

1 H1 111

11_() \

i

112

113

VLAN B

121

122 VLAN C

H6 131

H7 ' H8 132

133

FIG. 1 (Prior Art)

u

US. Patent

Sep. 7, 2010

Sheet 2 of3

US 7,792,058 B1

Gateway @

L3 Switch 83

E 8N1

8N2

“24>

8N3

“25o VLAN D

H1 \( H2f\ H3 211

212

L0.

213 VLANE

(H1f H21 H3 \ \ \ 241

242

24_0

243 \/

VLAN F

FIG. 2 (Prior Art)

US. Patent

Sep. 7, 2010

Sheet 3 of3

US 7,792,058 B1

INTERNET 301 SUPERVLAN x

SUPER VLAN Y

GATEWAY

&

3%

§_0

A

A

> L3 SWITCH 33

sNs 192.12

Q ‘

VIRTUAL ROUTER INTERFACE

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SUPER-VLAN Z

8N4 Broadcast Addresses 360 361 --192.1.1.0 All Zeroes 362 -- 192.1.1255

\

All Ones

FIG. 3

i

35 i

_

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US 7,792,058 B1 1

2

METHOD AND SYSTEM FOR VLAN AGGREGATION

are often referred to as broadcast domains. VLANs avoid

Wasting bandWidth caused by unnecessarily forWarding traf ?c to sWitches for Which there are no potential recipients (i.e. sWitches that do not have ports belonging to that particular

This application is a Continuation of, and claims the bene?t of, application Ser. No. 09/595,608 ?led Jun. 16, 2000, now US. Pat. No. 6,914,905.

VLAN, or that do not connect to hosts belonging to the same

BACKGROUND OF THE INVENTION

VLAN B 120, but does have ports belonging to VLAN C 130.

subnet). For example, With reference to FIG. 1, layer-2 sWitch S2 150 does not have any ports belonging to VLANA 110 or

Thus, traf?c originating fromports belonging to VLANA 110 1. Field of the Invention The present invention relates to the ?eld of virtual local area netWork (VLAN) topologies and intemetWork commu

orVLAN B 120 is not forWarded to layer-2 sWitch S2 150, but traf?c originating from port P6 140 VLAN C 130 is for Warded to layer-2 sWitch S2 150 ports P1 151 and P2 152. The subnet address that is commonly used as the basis for de?ning the layer-3 VLANs is a type of Internet Protocol address (IP address) used to route data packets across hetero

nications technologies. In particular, the present invention relates to an aggregated VLAN netWork architecture used in

forwarding data packets by a LAN sWitch connecting mul tiple VLANs. 2. Background Information and Description of RelatedArt

geneous netWorks. IP addresses are 32-bit numbers that have a tWo-level structure: a netWork number and a host number.

AVLAN is a logical grouping of netWorked host comput

The netWork number uniquely identi?es the netWork through

ers on some other basis than the physical netWork location

(e. g. department, primary application). VLANs alloW net

20

Work managers to more easily manage dynamic netWorks Where the identity and location of the netWork’s users are

requiring access to the Internet has groWn, a third level Was

constantly changing.

introduced into Internet routing protocols to augment the original tWo-level addressing structure. This third level

VLANs can be implemented in a number of different Ways,

depending on the netWork strategy. A prior art traditional layer-2 VLAN is based on a logical grouping of the layer-2 sWitch ports to Which the hosts connect. Alternative prior art

25

de?nes a sub-netWork, or “subnet.”

A subnet address may represent all the hosts at one geo graphic location, in one building, or on the same LAN or

layer-2 VLANs de?ne VLAN membership by the host’s Media Access Control (MAC) layer address. An example of a port-based prior art VLAN is shoWn in FIG. 1. As illustrated,

Which the host connects to the Internet, and the host number uniquely identi?es the address, or location, of the host on that uniquely identi?ed netWork. As the number of netWorks

VLAN. An advantage to dividing a netWork into subnets is that it alloWs an organiZation (such as an ISP) to be connected 30

to the Internet With a single shared netWork address. As a

VLANA 110 is de?ned as the set ofhosts H1 111, H2 112,

consequence, only one IP netWork address need be exported

and H3 113 that respectively connect to layer-2 sWitch S1 140

by routing protocols for all subnets belonging to a particular netWork, thereby reducing the routing overhead of the Inter

ports P1 141, P2 142, and P3 143. VLAN B 120 is de?ned as the set of hosts H4 121 and H5 122 that respectively connect to layer-2 sWitch S1 140 ports P4 144 and P5 145. Prior art second-generation VLANs can also span multiple sWitches

net. Without subnets, an ISP could get multiple connections to 35

the Internet, one for each of its logically separate netWorks,

connected by backbone 100. For example, as illustrated,

but this Would result in an inef?cient and unnecessary use of the limited number of unique netWork numbers, as Well as an

VLAN C 130 is de?ned as the set ofhosts H6 131, H7 132, and H8 133 that respectively connect to layer-2 sWitch S1 140

needed to properly route data packets from one netWork to

ports P6 146 and layer-2 sWitch S2 150 ports P1 151 and P2

unnecessary increase in the siZe of the global routing tables

152.

another. The standard procedure for creating and identifying subnets is provided in Internet Request For Comments (RFC)

Subsequent generations of prior art VLANs are embodied in layer-3 sWitches. Prior art layer-3 VLANs include VLANs based on the protocol type in a multi-protocol environment, or

950. Like VLANs, subnets can be used to contain netWork broadcast tra?ic, i.e. data packets from one subnet can be

40

on a netWork-layer address such as an Internet Protocol (IP) 45 broadcast only to other hosts in the same subnet by using the multicast group, or a subnet address in a Transmission Con appropriate broadcast IP addresses and routing protocols. In

trol Protocol (TCP)/IP netWork environment. An example of a prior art layer-3 VLAN based on subnet address is shoWn in FIG. 2. As illustrated, VLAN D 210 is de?ned as the set of hosts H1 211, H2 212 and H3 213 on subnet SN1 220 that connects to layer-3 sWitch S3 230, Which in turn connects to gateWay 200. VLAN E 240 is de?ned as the set of hosts H4 241, H5 242 and H6 243 on subnet SN2 250 that connects to layer-3 sWitch S3 230, and so forth.

An advantage of prior art VLANs based on layer-3 infor

addition, a data packet can be broadcast to a speci?c subnet. In this Way, a subnet is also considered a broadcast domain. 50

55

mation such as the subnet address, is that it alloWs hosts to

hosts belonging to the same subnet. For this reason, VLANs

rate VLAN based on a unique subnet address Within the ISP’ s oWn IP address netWork space. HoWever, there are a number

of draWbacks to assigning each subscriber their oWn VLAN based on a unique subnet address.

move to a different physical port on the sWitch in the same

VLAN Without having to recon?gure the ho st IP addresses. In an Internet Service Provider (I SP) environment, VLAN mem bership is often based on the subnet address for this reason, among others. An advantage of all prior art VLANs is that the layer-2 or layer-3 sWitch is able to use VLAN membership to contain netWork tra?ic. For example, tra?ic originating on one port is only sWitched to other ports belonging to the same VLAN, or tra?ic originating on one subnet is only sWitched to other

A typical use of the prior art layer-3 VLAN sWitches is in an ISP environment, Where VLAN membership may be based on netWork layer information such as the layer-3 protocol type or layer-3 subnet address as previously described. Tra ditionally, the ISP assigns each of their subscribers to a sepa

60

65

One draWback is that implementations of a subnet address ing scheme must set aside certain special purpose IP addresses that cannot be used for host IP addresses. The special purpose IP addresses include at least tWo different broadcast IP addresses, a default router address (i.e. the address of the default gateWay for the subnet), and, in an ISP environment, at least one IP address for a subscriber node. The tWo broadcast IP addresses that must be set aside are

?xed addresses With functional signi?cance, i.e. they are used to broadcast data packets to the subnet. One is the “all hosts”

US 7,792,058 B1 3

4

address, consisting of the network number, subnet number,

cannot be assigned to a host, but rather must be set aside for

and all ones in the host number ?eld. This address has the

broadcast or other special purposes.)

effect of transmitting the data packet to all of the hosts af?li ated With that subnet. The other is the “this network” address, consisting of the netWork number, subnet number, and all

Standard subnetting protocols require that the subnet mask be stored and compared by the router interface against the

Zeroes in the host number ?eld. This address has the effect of

data packets to determine Whether they can be sent directly to

transmitting the data packet to the subnet only. The broad

the destination on the local netWork or if they must be sent to a gateWay. Therefore, the use of subnets results in an unavoid

casting IP addresses are useful When a host needs to request information but does not knoW exactly Where to get it, or When a host needs to announce information to all other hosts

able amount of subnet mask storage and processing overhead that must be incurred When forWarding and routing data pack

on a subnet.

ets.

As a result of having to set aside these four types of special purpose and broadcast IP addresses, the IP address space

Yet another draWback to assigning each subscriber their oWn individual subnet is the constraints on the number and

overhead of subnets can become quite large, particularly

siZe of subnets imposed by the subnet addressing scheme itself. Since subnets must be de?ned along binary boundaries

When dividing a given IP netWork address space up into several smaller subnets, as is often the case in an ISP envi

ronment. For example, Table 1 illustrates the addressing over head for an ISP that allocates 8 subnets to its subscribers, With each subnet being a /27 netWork (Where the forWard-slash notation refers to the length of the combined netWork number/

that yield host address blocks in poWers of tWo, an ISP can only de?ne as many subnets as Will accommodate the host 20

address space needed by the largest subnet. For example, a / 24 netWork address space (Class C netWork) could be subnetted into 23 or 8/27 subnets, each supporting 25, or 32 hosts, minus

25

the largest subnet requires 50 host addresses, then the /24 netWork address space (Class C netWork) instead can only be divided into 22 or 4/26 subnets, each supporting (26-2), or 62 hosts. Even larger host address spaces, say 500-1000 hosts,

subnet number pre?x of the IP address).

at least the tWo broadcast addresses, for a total of 30 hosts. If TABLE 1 IP Address

# of individual

# of Special Purpose

Pre?x length

Addresses Available

Addresses Required

/27

32 x 8 subnets = 256

4 x 8 subnets = 32

Would need their oWn /22 or /23 subnet carved out of a /l6

netWork address space (Class B netWork). Since lSPs often

As can be seen, each /27 netWork is capable of supporting

service subscribers of varying and unpredictable siZe, assign

only 28 hosts, because 4 of the potentially available host

ing each subscriber an individual subnet can result in

addresses must be set aside for the broadcast addresses, default router, and subscriber node. For the 8 subnets, this results in a greater than 12.5% loss in potential address space

(32/256>